Implanted medical devices, such as implanted pacemakers, defibrillators or cardioverters, are programmed to perform various functions in response to cardiac episode data measured by various physiological sensors. The response of the implanted medical devices to measured cardiac episode data and other physiological data can be tailored by a physician to suit the needs of individual patients. In order to determine whether the implanted medical device is programmed properly, the physician directs the device to store measured cardiac episode data in memory. The cardiac episode data is transmitted from the implanted medical device to an external programmer device, for review by the physician.
Implanted medical devices, however, have a limited memory capacity for storage of cardiac episode data, e.g., electrograms, markers, episode classifications and the like, as well as other pertinent information, such as delivered therapies. Due to the limited memory capacity, the implanted medical devices typically are programmed to store certain pieces of information, such as certain segments of episode data in order to conserve memory. The physician programs the implanted device, for example, to store episode data that would be most valuable to the physician in order to diagnose the patient's condition and adjust the settings of the implanted medical device to prevent future cardiac episodes. Ordinarily, the implanted medical device is programmed to overwrite segments of episode data previously stored in the memory with new episode data when the memory is full.